27/09/06 D. FenechJodrell Bank Observatory

Supernova Remnants in the Supernova Remnants in the Central Starburst Region of M82Central Starburst Region of M82

EVN Symposium 2006

27/09/06 D. FenechJodrell Bank Observatory

Introduction

• M82 is one of the closest starburst galaxies.• First radio observations 1972 (Kronberg & Wilkinson

1975).• Ref. Tom’s Talk!• ~50 known sources in the central kpc, supernova

remnants and HII regions.• Talk will focus on a few compact sources – VLBI

observations.• Also discuss VLBI+MERLIN observations!

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VLBI

• VLBI observations have concentrated on four most compact sources – 41.95+57.5, 43.31+59.2, 44.01+59.6 and 45.17+61.2. (Pedlar et al. 1999,

McDonald et al. 2001, Beswick et al. 2006.) • These sources remain relatively unresolved in

MERLIN observations.• Expansion studies of 41.95+57.5 and 43.31+59.2

using EVN observations from 1986 and 1997, as well as global VLBI observations from 1998 and 2001.

• Fifth epoch observed 3rd March 2005! (global VLBI)

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41.95+57.5• Most compact source in M82.• Peak flux decreasing by ~8.5% per year!• Bi-polar structure not typical of supernova

remnant. • Expanding at ~1500km/s

Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

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43.31+59.2

• Youngest remnant in M82, first observed in 1972.(Kronberg & Wilkinson 1975)

• Almost complete shell structure.• EVN and VLBI observations have followed it’s

expansion since 1986.• Expansion velocity ~10,500km/s

Previous epoch Images taken from Beswick et al. MNRAS 369, 1221, 2006

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43.31+59.2

• Fit various deceleration parameters to data.

• Size evolution: D=kTδ

(Huang et al. 1994)

• D size, T is the age, δ is the deceleration parameter.

• Birth date unknown but can constrain from first detection in 1972.

Sedov

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More VLBI

• 44.01+59.6 – partial shell structure

• 45.17+61.2 • 2005 images.• Will study expansion in

a similar fashion to 43.31+58.3.

45.17+61.2

44.01+59.6

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Combination

• Simultaneous observations of M82 at 1.6GHz using MERLIN seven element array on 3rd March 2005.

• Successfully combined the two datasets to produce images with angular resolutions from ~5-100 mas

• Images comparable to MERLIN deep integration observations at 5GHz with angular resolution 35mas.

• Study size and structure of ~30 remnants at 1.6GHz

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MERLIN Deep Integration 5GHz Observations

• MERLIN observations in 2002 1-28 April.• 8 day deep integration.• ~ 175 hours on source.• Rms ~ 17μJy beam-1

• 2002 intended to be comparable to 1992 observations as well as a first epoch to future e-MERLIN observations.

• 1992 Observations 2-3 July• Rms ~ 46 μJy beam-1

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Combination

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A Personal Favourite

• 40.68+55.1 – largest detected remnant in M82.

• 129 mas at 5GHz corresponds to ~1.9 pc.

• Expansion of ~ 5000 km/s

1.6 GHz

5 GHz

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Conclusions

• Confirmed expansion of 43.31+58.3 at 1.6GHz.

• Continued observations of 41.95+57.5.

• Observe size and structure of a large number of sources at 1.6 GHz.

• Detailed comparison of sources at 5 and 1.6 GHz

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Background Image Credited to : NASA, ESA, CXC, and JPL-Caltech. Taken from the Hubble Gallery website.

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39.10+57.3

•Partial shell structure•110 mas at 5GHz•Expansion velocity ~